1
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Ulke J, Schwedler C, Krüger J, Stein V, Geserick P, Kleinridders A, Kappert K. High-fat diet alters N-glycosylation of PTPRJ in murine liver. J Nutr Biochem 2024; 123:109500. [PMID: 37875230 DOI: 10.1016/j.jnutbio.2023.109500] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 10/10/2023] [Accepted: 10/21/2023] [Indexed: 10/26/2023]
Abstract
Protein tyrosine phosphatases (PTPs) regulate multiple signaling pathways. Disruption of tyrosine phosphorylation through imbalanced action between protein tyrosine kinases (RTKs) and PTPs is a hallmark of metabolic disorders, including insulin resistance. A representative member of the receptor-type PTP family, PTPRJ (DEP-1), was previously identified as a negative regulator of insulin signaling and possesses post-translational glycosylation sites. In this regard, it seems of great importance to decipher the structure of PTPRJ's glycosylation, particularly in the context of metabolic disturbances, but this has not been done in detail. Thus, here we aimed at characterizing the glycosylation pattern of PTPRJ in liver. We show that N-glycosylation accounts for up to half of PTPRJ's molecular weight. Applying mass spectrometry, we detected increased levels of high-mannose structures in PTPRJ in liver tissue of obese mice compared to lean littermates. In addition, complex neutral structures without fucose were also elevated in PTPRJ of high-fat diet (HFD) mice. Conversely, complex fucosylated N-glycans as well as sialylated bi- and triantennary N-glycans, were significantly reduced in PTPRJ of HFD-derived liver tissue compared to LFD by ∼two fold (P≤.01, P≤.0001 and P≤.001, respectively). In congruence with these findings, the mannosidase MAN2A1, responsible for the conversion of high-mannose to complex N-glycans, was significantly downregulated under HFD conditions. Here we present for the first time that HFD-induced obesity impacts on the glycosylation pattern of the insulin signaling component PTPRJ in liver. These findings may inspire new research on the glycosylation of PTPs in metabolic diseases and may open up new therapeutic approaches.
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Affiliation(s)
- Jannis Ulke
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Diagnostic Laboratory Medicine, Clinical Chemistry and Pathobiochemistry, Augustenburger Platz 1, 13353 Berlin, Germany; Charité - Universitätsmedizin Berlin, Max Rubner Center (MRC) for Cardiovascular Metabolic Renal Research, Berlin, Germany
| | - Christian Schwedler
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Diagnostic Laboratory Medicine, Clinical Chemistry and Pathobiochemistry, Augustenburger Platz 1, 13353 Berlin, Germany
| | - Janine Krüger
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Diagnostic Laboratory Medicine, Clinical Chemistry and Pathobiochemistry, Augustenburger Platz 1, 13353 Berlin, Germany; Charité - Universitätsmedizin Berlin, Max Rubner Center (MRC) for Cardiovascular Metabolic Renal Research, Berlin, Germany
| | - Vanessa Stein
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Diagnostic Laboratory Medicine, Clinical Chemistry and Pathobiochemistry, Augustenburger Platz 1, 13353 Berlin, Germany; Charité - Universitätsmedizin Berlin, Max Rubner Center (MRC) for Cardiovascular Metabolic Renal Research, Berlin, Germany
| | - Peter Geserick
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Diagnostic Laboratory Medicine, Clinical Chemistry and Pathobiochemistry, Augustenburger Platz 1, 13353 Berlin, Germany; Charité - Universitätsmedizin Berlin, Max Rubner Center (MRC) for Cardiovascular Metabolic Renal Research, Berlin, Germany
| | - André Kleinridders
- Department of Molecular and Experimental Nutritional Medicine, Institute of Nutritional Science, University of Potsdam, Nuthetal, Germany
| | - Kai Kappert
- Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin and Humboldt-Universität zu Berlin, Institute of Diagnostic Laboratory Medicine, Clinical Chemistry and Pathobiochemistry, Augustenburger Platz 1, 13353 Berlin, Germany; Charité - Universitätsmedizin Berlin, Max Rubner Center (MRC) for Cardiovascular Metabolic Renal Research, Berlin, Germany.
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2
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Schwarz M, Rizzo S, Paz WE, Kresinsky A, Thévenin D, Müller JP. Disrupting PTPRJ transmembrane-mediated oligomerization counteracts oncogenic receptor tyrosine kinase FLT3 ITD. Front Oncol 2022; 12:1017947. [PMID: 36452504 PMCID: PMC9701752 DOI: 10.3389/fonc.2022.1017947] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Accepted: 10/25/2022] [Indexed: 11/15/2022] Open
Abstract
The receptor protein tyrosine phosphatase (RPTP) PTPRJ (also known as DEP-1) has been identified as a negative regulator of the receptor tyrosine kinase FLT3 signalling in vitro. The inactivation of the PTPRJ gene in mice expressing the constitutively active, oncogenic receptor tyrosine kinase FLT3 ITD aggravated known features of leukaemogenesis, revealing PTPRJ's antagonistic role. FLT3 ITD mutations resulting in constitutively kinase activity and cell transformation frequently occur in patients with acute myeloid leukaemia (AML). Thus, in situ activation of PTPRJ could be used to abrogate oncogenic FLT3 signalling. The activity of PTPRJ is suppressed by homodimerization, which is mediated by transmembrane domain (TMD) interactions. Specific Glycine-to-Leucine mutations in the TMD disrupt oligomerization and inhibit the Epidermal Growth Factor Receptor (EGFR) and EGFR-driven cancer cell phenotypes. To study the effects of PTPRJ TMD mutant proteins on FLT3 ITD activity in cell lines, endogenous PTPRJ was inactivated and replaced by stable expression of PTPRJ TMD mutants. Autophosphorylation of wild-type and ITD-mutated FLT3 was diminished in AML cell lines expressing the PTPRJ TMD mutants compared to wild-type-expressing cells. This was accompanied by reduced FLT3-mediated global protein tyrosine phosphorylation and downstream signalling. Further, PTPRJ TMD mutant proteins impaired the proliferation and in vitro transformation of leukemic cells. Although PTPRJ's TMD mutant proteins showed impaired self-association, the specific phosphatase activity of immunoprecipitated proteins remained unchanged. In conclusion, this study demonstrates that the destabilization of PTPRJ TMD-mediated self-association increases the activity of PTPRJ in situ and impairs FLT3 activity and FLT3-driven cell phenotypes of AML cells. Thus, disrupting the oligomerization of PTPRJ in situ could prove a valuable therapeutic strategy to restrict oncogenic FLT3 activity in leukemic cells.
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Affiliation(s)
- Marie Schwarz
- Institute for Molecular Cell Biology, CMB - Center for Molecular Biomedicine, University Hospital Jena, Jena, Germany
| | - Sophie Rizzo
- Department of Chemistry, Lehigh University, Bethlehem, PA, United States
| | | | - Anne Kresinsky
- Institute for Molecular Cell Biology, CMB - Center for Molecular Biomedicine, University Hospital Jena, Jena, Germany,Leibniz Institute on Aging, Fritz Lipmann Institute, Jena, Germany
| | - Damien Thévenin
- Department of Chemistry, Lehigh University, Bethlehem, PA, United States
| | - Jörg P. Müller
- Institute for Molecular Cell Biology, CMB - Center for Molecular Biomedicine, University Hospital Jena, Jena, Germany,*Correspondence: Jörg P. Müller,
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3
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Bloch E, Sikorski EL, Pontoriero D, Day EK, Berger BW, Lazzara MJ, Thévenin D. Disrupting the transmembrane domain-mediated oligomerization of protein tyrosine phosphatase receptor J inhibits EGFR-driven cancer cell phenotypes. J Biol Chem 2019; 294:18796-18806. [PMID: 31676686 DOI: 10.1074/jbc.ra119.010229] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 10/21/2019] [Indexed: 12/19/2022] Open
Abstract
Receptor protein tyrosine phosphatases (RPTPs) play critical regulatory roles in mammalian signal transduction. However, the structural basis for the regulation of their catalytic activity is not fully understood, and RPTPs are generally not therapeutically targetable. This knowledge gap is partially due to the lack of known natural ligands or selective agonists of RPTPs. Contrary to what is known from structure-function studies of receptor tyrosine kinases (RTKs), RPTP activities have been reported to be suppressed by dimerization, which may prevent RPTPs from accessing their RTK substrates. We report here that homodimerization of protein tyrosine phosphatase receptor J (PTPRJ, also known as DEP-1) is regulated by specific transmembrane (TM) residues. We found that disrupting these interactions destabilizes homodimerization of full-length PTPRJ in cells, reduces the phosphorylation of the known PTPRJ substrate epidermal growth factor receptor (EGFR) and of other downstream signaling effectors, antagonizes EGFR-driven cell phenotypes, and promotes substrate access. We demonstrate these observations in human cancer cells using mutational studies and identified a peptide that binds to the PTPRJ TM domain and represents the first example of an allosteric agonist of RPTPs. The results of our study provide fundamental structural and functional insights into how PTPRJ activity is tuned by TM interactions in cells. Our findings also open up opportunities for developing peptide-based agents that could be used as tools to probe RPTPs' signaling mechanisms or to manage cancers driven by RTK signaling.
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Affiliation(s)
- Elizabeth Bloch
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015
| | - Eden L Sikorski
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015
| | - David Pontoriero
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22903
| | - Evan K Day
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22903
| | - Bryan W Berger
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22903
| | - Matthew J Lazzara
- Department of Chemical Engineering, University of Virginia, Charlottesville, Virginia 22903
| | - Damien Thévenin
- Department of Chemistry, Lehigh University, Bethlehem, Pennsylvania 18015.
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4
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Bilotta A, Dattilo V, D'Agostino S, Belviso S, Scalise S, Bilotta M, Gaudio E, Paduano F, Perrotti N, Florio T, Fusco A, Iuliano R, Trapasso F. A novel splice variant of the protein tyrosine phosphatase PTPRJ that encodes for a soluble protein involved in angiogenesis. Oncotarget 2018; 8:10091-10102. [PMID: 28052032 PMCID: PMC5354644 DOI: 10.18632/oncotarget.14350] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2016] [Accepted: 12/13/2016] [Indexed: 02/01/2023] Open
Abstract
PTPRJ is a receptor protein tyrosine phosphatase with tumor suppressor activity. Very little is known about the role of PTPRJ ectodomain, although recently both physiological and synthetic PTPRJ ligands have been identified. A putative shorter spliced variant, coding for a 539 aa protein corresponding to the extracellular N-terminus of PTPRJ, is reported in several databases but, currently, no further information is available. Here, we confirmed that the PTPRJ short isoform (named sPTPRJ) is a soluble protein secreted into the supernatant of both endothelial and tumor cells. Like PTPRJ, also sPTPRJ undergoes post-translational modifications such as glycosylation, as assessed by sPTPRJ immunoprecipitation. To characterize its functional activity, we performed an endothelial cell tube formation assay and a wound healing assay on HUVEC cells overexpressing sPTPRJ and we found that sPTPRJ has a proangiogenic activity. We also showed that sPTPRJ expression down-regulates endothelial adhesion molecules, that is a hallmark of proangiogenic activity. Moreover, sPTPRJ mRNA levels in human high-grade glioma, one of the most angiogenic tumors, are higher in tumor samples compared to controls. Further studies will be helpful not only to clarify the way sPTPRJ works but also to supply clues to circumvent its activity in cancer therapy.
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Affiliation(s)
- Anna Bilotta
- Department of Medicina Sperimentale e Clinica, University Magna Graecia of Catanzaro, Catanzaro, Italy
| | - Vincenzo Dattilo
- Department of Scienze della Salute, University Magna Graecia of Catanzaro, Catanzaro, Italy
| | - Sabrina D'Agostino
- Department of Medicina Sperimentale e Clinica, University Magna Graecia of Catanzaro, Catanzaro, Italy
| | - Stefania Belviso
- Department of Medicina Sperimentale e Clinica, University Magna Graecia of Catanzaro, Catanzaro, Italy
| | - Stefania Scalise
- Department of Medicina Sperimentale e Clinica, University Magna Graecia of Catanzaro, Catanzaro, Italy
| | - Mariaconcetta Bilotta
- Department of Medicina Sperimentale e Clinica, University Magna Graecia of Catanzaro, Catanzaro, Italy
| | - Eugenio Gaudio
- Department of Medicina Sperimentale e Clinica, University Magna Graecia of Catanzaro, Catanzaro, Italy.,Lymphoma and Genomics Research Program, Institute of Oncology Research (IOR), Bellinzona, Switzerland
| | - Francesco Paduano
- Department of Medicina Sperimentale e Clinica, University Magna Graecia of Catanzaro, Catanzaro, Italy.,Tecnologica Research Institute, Biomedical Section, Crotone, Italy
| | - Nicola Perrotti
- Department of Scienze della Salute, University Magna Graecia of Catanzaro, Catanzaro, Italy
| | - Tullio Florio
- Laboratory of Pharmacology, Dept. of Internal Medicine, and Center of Excellence for Biomedical Research (CEBR), University of Genova, Genova, Italy
| | - Alfredo Fusco
- Istituto di Endocrinologia e Oncologia Sperimentale - CNR c/o Dipartimento di Medicina Molecolare e Biotecnologie Mediche, University Federico II of Napoli, Napoli, Italy
| | - Rodolfo Iuliano
- Department of Medicina Sperimentale e Clinica, University Magna Graecia of Catanzaro, Catanzaro, Italy
| | - Francesco Trapasso
- Department of Medicina Sperimentale e Clinica, University Magna Graecia of Catanzaro, Catanzaro, Italy
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5
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Ortuso F, Paduano F, Carotenuto A, Gomez-Monterrey I, Bilotta A, Gaudio E, Sala M, Artese A, Vernieri E, Dattilo V, Iuliano R, Brancaccio D, Bertamino A, Musella S, Alcaro S, Grieco P, Perrotti N, Croce CM, Novellino E, Fusco A, Campiglia P, Trapasso F. Discovery of PTPRJ agonist peptides that effectively inhibit in vitro cancer cell proliferation and tube formation. ACS Chem Biol 2013; 8:1497-506. [PMID: 23627474 DOI: 10.1021/cb3007192] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
PTPRJ is a receptor protein tyrosine phosphatase involved in both physiological and oncogenic pathways. We previously reported that its expression is strongly reduced in the majority of explored cancer cell lines and tumor samples; moreover, its restoration blocks in vitro cancer cell proliferation and in vivo tumor formation. By means of a phage display library screening, we recently identified two peptides able to bind and activate PTPRJ, resulting in cell growth inhibition and apoptosis of both cancer and endothelial cells. Here, on a previously discovered PTPRJ agonist peptide, PTPRJ-pep19, we synthesized and assayed a panel of nonapeptide analogues with the aim to identify specific amino acid residues responsible for peptide activity. These second-generation nonapeptides were tested on both cancer and primary endothelial cells (HeLa and HUVEC, respectively); interestingly, one of them (PTPRJ-19.4) was able to both dramatically reduce cell proliferation and effectively trigger apoptosis of both HeLa and HUVECs compared to its first-generation counterpart. Moreover, PTPRJ-pep19.4 significantly inhibited in vitro tube formation on Matrigel. Intriguingly, while ERK1/2 phosphorylation and cell proliferation were both inhibited by PTPRJ-pep19.4 in breast cancer cells (MCF-7 and SKBr3), no effects were observed on primary normal human mammary endothelial cells (HMEC). We further characterized these peptides by molecular modeling and NMR experiments reporting, for the most active peptide, the possibility of self-aggregation states and highlighting new hints of structure-activity relationship. Thus, our results indicate that this nonapeptide might represent a great potential lead for the development of novel targeted anticancer drugs.
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Affiliation(s)
| | | | - Alfonso Carotenuto
- Dipartimento
di Farmacia, Università degli Studi di Napoli “Federico II”, 80131 Napoli, Italy
| | - Isabel Gomez-Monterrey
- Dipartimento
di Farmacia, Università degli Studi di Napoli “Federico II”, 80131 Napoli, Italy
| | | | - Eugenio Gaudio
- Department of Molecular Virology,
Immunology and Medical Genetics and Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, United
States
| | - Marina Sala
- Dipartimento
di Farmacia, Università degli Studi di Napoli “Federico II”, 80131 Napoli, Italy
| | | | | | | | | | - Diego Brancaccio
- Dipartimento
di Farmacia, Università degli Studi di Napoli “Federico II”, 80131 Napoli, Italy
| | - Alessia Bertamino
- Dipartimento di
Farmacia, Università di Salerno,
84084 Fisciano, Italy
| | - Simona Musella
- Dipartimento di
Farmacia, Università di Salerno,
84084 Fisciano, Italy
| | | | - Paolo Grieco
- Dipartimento
di Farmacia, Università degli Studi di Napoli “Federico II”, 80131 Napoli, Italy
| | | | - Carlo M. Croce
- Department of Molecular Virology,
Immunology and Medical Genetics and Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, United
States
| | - Ettore Novellino
- Dipartimento
di Farmacia, Università degli Studi di Napoli “Federico II”, 80131 Napoli, Italy
| | - Alfredo Fusco
- Dipartimento
di Biologia e Patologia Cellulare e Molecolare c/o Istituto di Endocrinologia
ed Oncologia Sperimentale del CNR, Università degli Studi di Napoli “Federico II”, 80131
Napoli, Italy
| | - Pietro Campiglia
- Dipartimento di
Farmacia, Università di Salerno,
84084 Fisciano, Italy
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6
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Paduano F, Ortuso F, Campiglia P, Raso C, Iaccino E, Gaspari M, Gaudio E, Mangone G, Carotenuto A, Bilotta A, Narciso D, Palmieri C, Agosti V, Artese A, Gomez-Monterrey I, Sala M, Cuda G, Iuliano R, Perrotti N, Scala G, Viglietto G, Alcaro S, Croce CM, Novellino E, Fusco A, Trapasso F. Isolation and functional characterization of peptide agonists of PTPRJ, a tyrosine phosphatase receptor endowed with tumor suppressor activity. ACS Chem Biol 2012; 7:1666-76. [PMID: 22759068 DOI: 10.1021/cb300281t] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
PTPRJ is a receptor-type protein tyrosine phosphatase whose expression is strongly reduced in the majority of investigated cancer cell lines and tumor specimens. PTPRJ negatively interferes with mitogenic signals originating from several oncogenic receptor tyrosine kinases, including HGFR, PDGFR, RET, and VEGFR-2. Here we report the isolation and characterization of peptides from a random peptide phage display library that bind and activate PTPRJ. These agonist peptides, which are able to both circularize and form dimers in acqueous solution, were assayed for their biochemical and biological activity on both human cancer cells and primary endothelial cells (HeLa and HUVEC, respectively). Our results demonstrate that binding of PTPRJ-interacting peptides to cell cultures dramatically reduces the extent of both MAPK phosphorylation and total phosphotyrosine levels; conversely, they induce a significant increase of the cell cycle inhibitor p27(Kip1). Moreover, PTPRJ agonist peptides both reduce proliferation and trigger apoptosis of treated cells. Our data indicate that peptide agonists of PTPRJ positively modulate the PTPRJ activity and may lead to novel targeted anticancer therapies.
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Affiliation(s)
- Francesco Paduano
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
| | - Francesco Ortuso
- Laboratorio
di Chimica Farmaceutica
Computazionale, Dipartimento di Scienze Farmacobiologiche, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100 Catanzaro, Italy
| | - Pietro Campiglia
- Dipartimento di Scienze Farmaceutiche
e Biomediche, Sezione Chimico-Tecnologica, Università di Salerno, 84084 Fisciano (Salerno), Italy
| | - Cinzia Raso
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
| | - Enrico Iaccino
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
| | - Marco Gaspari
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
| | - Eugenio Gaudio
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
- Department of Molecular Virology,
Immunology and Medical Genetics and Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, United
States
| | - Graziella Mangone
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
| | - Alfonso Carotenuto
- Dipartimento di
Chimica Farmaceutica
e Tossicologica, Università degli Studi di Napoli “Federico II”, 80131 Naples, Italy
| | - Anna Bilotta
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
| | - Domenico Narciso
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
| | - Camillo Palmieri
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
| | - Valter Agosti
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
| | - Anna Artese
- Laboratorio
di Chimica Farmaceutica
Computazionale, Dipartimento di Scienze Farmacobiologiche, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100 Catanzaro, Italy
| | - Isabel Gomez-Monterrey
- Dipartimento di
Chimica Farmaceutica
e Tossicologica, Università degli Studi di Napoli “Federico II”, 80131 Naples, Italy
| | - Marina Sala
- Dipartimento di Scienze Farmaceutiche
e Biomediche, Sezione Chimico-Tecnologica, Università di Salerno, 84084 Fisciano (Salerno), Italy
| | - Giovanni Cuda
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
| | - Rodolfo Iuliano
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
| | - Nicola Perrotti
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
| | - Giuseppe Scala
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
| | - Giuseppe Viglietto
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
| | - Stefano Alcaro
- Laboratorio
di Chimica Farmaceutica
Computazionale, Dipartimento di Scienze Farmacobiologiche, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100 Catanzaro, Italy
| | - Carlo M. Croce
- Department of Molecular Virology,
Immunology and Medical Genetics and Comprehensive Cancer Center, The Ohio State University, Columbus, Ohio 43210, United
States
| | - Ettore Novellino
- Dipartimento di
Chimica Farmaceutica
e Tossicologica, Università degli Studi di Napoli “Federico II”, 80131 Naples, Italy
| | - Alfredo Fusco
- Dipartimento di Biologia e Patologia
Cellulare e Molecolare c/o Istituto di Endocrinologia ed Oncologia
Sperimentale del CNR, Università degli Studi di Napoli “Federico II”, 80131 Naples, Italy
| | - Francesco Trapasso
- Dipartimento di Medicina Sperimentale
e Clinica, Università “Magna Græcia” di Catanzaro, Campus “S. Venuta”, 88100
Catanzaro, Italy
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7
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Receptor type protein tyrosine phosphatases (RPTPs) - roles in signal transduction and human disease. J Cell Commun Signal 2012; 6:125-38. [PMID: 22851429 DOI: 10.1007/s12079-012-0171-5] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2012] [Accepted: 07/12/2012] [Indexed: 01/06/2023] Open
Abstract
Protein tyrosine phosphorylation is a fundamental regulatory mechanism controlling cell proliferation, differentiation, communication, and adhesion. Disruption of this key regulatory mechanism contributes to a variety of human diseases including cancer, diabetes, and auto-immune diseases. Net protein tyrosine phosphorylation is determined by the dynamic balance of the activity of protein tyrosine kinases (PTKs) and protein tyrosine phosphatases (PTPs). Mammals express many distinct PTKs and PTPs. Both of these families can be sub-divided into non-receptor and receptor subtypes. Receptor protein tyrosine kinases (RPTKs) comprise a large family of cell surface proteins that initiate intracellular tyrosine phosphorylation-dependent signal transduction in response to binding of extracellular ligands, such as growth factors and cytokines. Receptor-type protein tyrosine phosphatases (RPTPs) are enzymatic and functional counterparts of RPTKs. RPTPs are a family of integral cell surface proteins that possess intracellular PTP activity, and extracellular domains that have sequence homology to cell adhesion molecules. In comparison to extensively studied RPTKs, much less is known about RPTPs, especially regarding their substrate specificities, regulatory mechanisms, biological functions, and their roles in human diseases. Based on the structure of their extracellular domains, the RPTP family can be grouped into eight sub-families. This article will review one representative member from each RPTP sub-family.
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8
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Smart CE, Askarian Amiri ME, Wronski A, Dinger ME, Crawford J, Ovchinnikov DA, Vargas AC, Reid L, Simpson PT, Song S, Wiesner C, French JD, Dave RK, da Silva L, Purdon A, Andrew M, Mattick JS, Lakhani SR, Brown MA, Kellie S. Expression and function of the protein tyrosine phosphatase receptor J (PTPRJ) in normal mammary epithelial cells and breast tumors. PLoS One 2012; 7:e40742. [PMID: 22815804 PMCID: PMC3398958 DOI: 10.1371/journal.pone.0040742] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 06/12/2012] [Indexed: 12/31/2022] Open
Abstract
The protein tyrosine phosphatase receptor J, PTPRJ, is a tumor suppressor gene that has been implicated in a range of cancers, including breast cancer, yet little is known about its role in normal breast physiology or in mammary gland tumorigenesis. In this paper we show that PTPRJ mRNA is expressed in normal breast tissue and reduced in corresponding tumors. Meta-analysis revealed that the gene encoding PTPRJ is frequently lost in breast tumors and that low expression of the transcript associated with poorer overall survival at 20 years. Immunohistochemistry of PTPRJ protein in normal human breast tissue revealed a distinctive apical localisation in the luminal cells of alveoli and ducts. Qualitative analysis of a cohort of invasive ductal carcinomas revealed retention of normal apical PTPRJ localization where tubule formation was maintained but that tumors mostly exhibited diffuse cytoplasmic staining, indicating that dysregulation of localisation associated with loss of tissue architecture in tumorigenesis. The murine ortholog, Ptprj, exhibited a similar localisation in normal mammary gland, and was differentially regulated throughout lactational development, and in an in vitro model of mammary epithelial differentiation. Furthermore, ectopic expression of human PTPRJ in HC11 murine mammary epithelial cells inhibited dome formation. These data indicate that PTPRJ may regulate differentiation of normal mammary epithelia and that dysregulation of protein localisation may be associated with tumorigenesis.
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MESH Headings
- Animals
- Breast Neoplasms/enzymology
- Breast Neoplasms/genetics
- Breast Neoplasms/pathology
- Cell Differentiation/genetics
- Cell Line, Tumor
- Down-Regulation/genetics
- Epithelial Cells/enzymology
- Epithelial Cells/pathology
- Epithelium/enzymology
- Epithelium/pathology
- Female
- Gene Dosage/genetics
- Gene Expression Regulation, Neoplastic
- Genetic Loci/genetics
- Humans
- Introns/genetics
- Mammary Glands, Animal/enzymology
- Mammary Glands, Animal/growth & development
- Mammary Glands, Animal/pathology
- Mammary Glands, Human/enzymology
- Mammary Glands, Human/pathology
- Mammary Neoplasms, Animal/enzymology
- Mammary Neoplasms, Animal/genetics
- Mammary Neoplasms, Animal/pathology
- Meta-Analysis as Topic
- Mice
- Mice, Inbred C57BL
- Pregnancy
- RNA, Antisense/genetics
- RNA, Long Noncoding/genetics
- RNA, Long Noncoding/metabolism
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptor-Like Protein Tyrosine Phosphatases, Class 3/genetics
- Receptor-Like Protein Tyrosine Phosphatases, Class 3/metabolism
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Affiliation(s)
- Chanel E. Smart
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
- Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia
- Queensland Institute of Medical Research, Brisbane, Queensland, Australia
| | - Marjan E. Askarian Amiri
- Institute for Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Ania Wronski
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Marcel E. Dinger
- Institute for Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Joanna Crawford
- Institute for Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Dmitry A. Ovchinnikov
- Institute for Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Ana Cristina Vargas
- Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia
- Queensland Institute of Medical Research, Brisbane, Queensland, Australia
| | - Lynne Reid
- Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia
- Queensland Institute of Medical Research, Brisbane, Queensland, Australia
| | - Peter T. Simpson
- Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia
- Queensland Institute of Medical Research, Brisbane, Queensland, Australia
| | - Sarah Song
- Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia
- Institute for Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Christiane Wiesner
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Juliet D. French
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Richa K. Dave
- Institute for Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Leonard da Silva
- Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia
- Queensland Institute of Medical Research, Brisbane, Queensland, Australia
| | - Amy Purdon
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
- Institute for Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Megan Andrew
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - John S. Mattick
- Institute for Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Sunil R. Lakhani
- Centre for Clinical Research, The University of Queensland, Brisbane, Queensland, Australia
- Queensland Institute of Medical Research, Brisbane, Queensland, Australia
- School of Medicine, The University of Queensland, Brisbane, Queensland, Australia
- University of Queensland, Department of Anatomical Pathology, Brisbane, Queensland, Australia
| | - Melissa A. Brown
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Stuart Kellie
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
- Institute for Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
- * E-mail:
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9
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Paduano F, Dattilo V, Narciso D, Bilotta A, Gaudio E, Menniti M, Agosti V, Palmieri C, Perrotti N, Fusco A, Trapasso F, Iuliano R. Protein tyrosine phosphatase PTPRJ is negatively regulated by microRNA-328. FEBS J 2012; 280:401-12. [PMID: 22564856 DOI: 10.1111/j.1742-4658.2012.08624.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Expression of PTPRJ, which is a ubiquitous receptor-type protein tyrosine phosphatase, is significantly reduced in a vast majority of human epithelial cancers and cancer cell lines (i.e. colon, lung, thyroid, mammary and pancreatic tumours). A possible role for microRNAs (miRNAs) in the negative regulation of PTPRJ expression has never been investigated. In this study, we show that overexpression of microRNA-328 (miR-328) decreases PTPRJ expression in HeLa and SKBr3 cells. Further investigations demonstrate that miR-328 acts directly on the 3'UTR of PTPRJ, resulting in reduced mRNA levels. Luciferase assay and site-specific mutagenesis were used to identify a functional miRNA response element in the 3'UTR of PTPRJ. Expression of miR-328 significantly enhances cell proliferation in HeLa and SKBr3 cells, similar to the effects of downregulation of PTPRJ with small interfering RNA. Additionally, in HeLa cells, the proliferative effect of miR-328 was not observed when PTPRJ was silenced with small interfering RNA; conversely, restoration of PTPRJ expression in miR-328-overexpressing cells abolished the proliferative activity of miR-328. In conclusion, we report the identification of miR-328 as an important player in the regulation of PTPRJ expression, and we propose that the interaction of miR-328 with PTPRJ is responsible for miR-328-dependent increase of epithelial cell proliferation.
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Affiliation(s)
- Francesco Paduano
- Dipartimento di Medicina Sperimentale e Clinica, Università Magna Graecia, Catanzaro, Italy.
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10
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Barbieri F, Würth R, Favoni RE, Pattarozzi A, Gatti M, Ratto A, Ferrari A, Bajetto A, Florio T. Receptor tyrosine kinase inhibitors and cytotoxic drugs affect pleural mesothelioma cell proliferation: insight into EGFR and ERK1/2 as antitumor targets. Biochem Pharmacol 2011; 82:1467-77. [PMID: 21787763 DOI: 10.1016/j.bcp.2011.07.073] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2011] [Revised: 07/04/2011] [Accepted: 07/06/2011] [Indexed: 11/15/2022]
Abstract
Malignant pleural mesothelioma (MPM) is an aggressive chemotherapy-resistant cancer. Up-regulation of epidermal growth factor receptor (EGFR) plays an important role in MPM development and EGFR-tyrosine kinase inhibitors (TKIs) may represent novel therapeutic options. We tested the effects of the EGFR TKIs gefitinib and erlotinib and TKIs targeted to other growth factors (VEGFR and PDGFR), in comparison to standard antineoplastic agents, in two human MPM cell lines, IST-Mes2 and ZL55. All drugs showed IC(50) values in the micromolar range: TKIs induced cytostatic effects at concentrations up to the IC(50,) while conventional drug growth-inhibitory activity was mainly cytotoxic. Moreover, the treatment of IST-Mes2 with TKIs (gefitinib and imatinib mesylate) in combination with cisplatin and gemcitabine did not show additivity. Focusing on the molecular mechanisms underlying the antiproliferative and pro-apoptotic effects of EGFR-TKIs, we observed that gefitinib induced the formation and stabilization of inactive EGFR homodimers, even in absence of EGF, as demonstrated by EGFR B(max) and number of sites/cell. The analysis of downstream effectors of EGFR signaling demonstrated that EGF-induced proliferation, reverted by gefitinib, involved ERK1/2 activation, independently from Akt pathway. Gefitinib inhibits MPM cell growth and survival, preventing EGF-dependent activation of ERK1/2 pathway by blocking EGFR-TK phosphorylation and stabilizing inactive EGFR dimers. Along with the molecular definition of TKIs pharmacological efficacy in vitro, these results may contribute to delve deep into the promising but still controversial role for targeted and conventional drugs in the therapy of MPM.
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Affiliation(s)
- Federica Barbieri
- Laboratory of Pharmacology, Department of Oncology, Biology and Genetics, University of Genova, Viale Benedetto XV, 2-16132 Genova, Italy.
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11
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Iuliano R, Palmieri D, He H, Iervolino A, Borbone E, Pallante P, Cianflone A, Nagy R, Alder H, Calin GA, Trapasso F, Giordano C, Croce CM, de la Chapelle A, Fusco A. Role of PTPRJ genotype in papillary thyroid carcinoma risk. Endocr Relat Cancer 2010; 17:1001-6. [PMID: 20823296 PMCID: PMC3915780 DOI: 10.1677/erc-10-0143] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The strong genetic predisposition to papillary thyroid carcinoma (PTC) might be due to a combination of low-penetrance susceptibility variants. Thus, the research into gene variants involved in the increase of susceptibility to PTC is a relevant field of investigation. The gene coding for the receptor-type tyrosine phosphatase PTPRJ has been proposed as a cancer susceptibility gene, and its role as a tumor suppressor gene is well established in thyroid carcinogenesis. In this study, we want to ascertain the role of PTPRJ genotype in the risk for PTC. We performed a case-control study in which we determined the PTPRJ genotype for the non-synonymous Gln276Pro and Asp872Glu polymorphisms by PCR amplification and sequencing. We calculated allele and genotype frequencies for the considered polymorphisms of PTPRJ in a total sample of 299 cases (PTC patients) and 339 controls (healthy subjects) selected from Caucasian populations. We observed a significantly higher frequency of homozygotes for the Asp872 allele in the group of PTC patients than in the control group (odds ratio=1.61, 95% confidence interval 1.15-2.25, P=0.0053). We observed a non-significant increased frequency of homozygotes for Gln276Pro polymorphism in PTC cases in two distinct Caucasian populations. Therefore, the results reported here show that the homozygous genotype for Asp872 of PTPRJ is associated with an increased risk to develop PTC.
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Affiliation(s)
- Rodolfo Iuliano
- Dipartimento di Medicina Sperimentale e Clinica, Facoltà di Medicina e Chirurgia, Università degli Studi “Magna Græcia” di Catanzaro, viale Europa, 88100 Catanzaro, Italy
- Corresponding Authors Rodolfo Iuliano, Dipartimento di Medicina Sperimentale e Clinica, Facoltà di Medicina e Chirurgia, Università di Catanzaro, Campus “Salvatore Venuta” Viale Europa, località Germaneto, 88100 Catanzaro, Italy. Tel. +39-0961-3695182 Fax: +39-0961-3694090 Istituto di Endocrinologia ed Oncologia Sperimentale del CNR c/o Dipartimento di Biologia e Patologia Cellulare e Molecolare c/o, Facoltà di Medicina e Chirurgia, Università degli Studi di Napoli “Federico II”,80131 Napoli, Italy. Tel. +39-081-3737857 Fax: +39-081-3737808
| | - Dario Palmieri
- Istituto di Endocrinologia ed Oncologia Sperimentale del CNR c/o Dipartimento di Biologia e Patologia Cellulare e Molecolare c/o, Facoltà di Medicina e Chirurgia, Università degli Studi di Napoli “Federico II”,80131 Napoli, Italy
- NOGEC (Naples Oncogenomic Center) – CEINGE, Biotecnologie Avanzate, via Comunale Margherita, 482, 80145 Napoli, Italy
| | - Huiling He
- Division of Human Cancer Genetics, Comprehensive Cancer Center, Ohio State University, 460 West 12th Avenue, Columbus, Ohio, 43210, USA
| | - Angela Iervolino
- Istituto di Endocrinologia ed Oncologia Sperimentale del CNR c/o Dipartimento di Biologia e Patologia Cellulare e Molecolare c/o, Facoltà di Medicina e Chirurgia, Università degli Studi di Napoli “Federico II”,80131 Napoli, Italy
- NOGEC (Naples Oncogenomic Center) – CEINGE, Biotecnologie Avanzate, via Comunale Margherita, 482, 80145 Napoli, Italy
| | - Eleonora Borbone
- Istituto di Endocrinologia ed Oncologia Sperimentale del CNR c/o Dipartimento di Biologia e Patologia Cellulare e Molecolare c/o, Facoltà di Medicina e Chirurgia, Università degli Studi di Napoli “Federico II”,80131 Napoli, Italy
- NOGEC (Naples Oncogenomic Center) – CEINGE, Biotecnologie Avanzate, via Comunale Margherita, 482, 80145 Napoli, Italy
| | - Pierlorenzo Pallante
- Istituto di Endocrinologia ed Oncologia Sperimentale del CNR c/o Dipartimento di Biologia e Patologia Cellulare e Molecolare c/o, Facoltà di Medicina e Chirurgia, Università degli Studi di Napoli “Federico II”,80131 Napoli, Italy
- NOGEC (Naples Oncogenomic Center) – CEINGE, Biotecnologie Avanzate, via Comunale Margherita, 482, 80145 Napoli, Italy
| | - Alessandra Cianflone
- Istituto di Endocrinologia ed Oncologia Sperimentale del CNR c/o Dipartimento di Biologia e Patologia Cellulare e Molecolare c/o, Facoltà di Medicina e Chirurgia, Università degli Studi di Napoli “Federico II”,80131 Napoli, Italy
| | - Rebecca Nagy
- Division of Human Cancer Genetics, Comprehensive Cancer Center, Ohio State University, 460 West 12th Avenue, Columbus, Ohio, 43210, USA
| | - Hansjuerg Alder
- Division of Human Cancer Genetics, Comprehensive Cancer Center, Ohio State University, 460 West 12th Avenue, Columbus, Ohio, 43210, USA
| | - George A. Calin
- Division of Human Cancer Genetics, Comprehensive Cancer Center, Ohio State University, 460 West 12th Avenue, Columbus, Ohio, 43210, USA
| | - Francesco Trapasso
- Dipartimento di Medicina Sperimentale e Clinica, Facoltà di Medicina e Chirurgia, Università degli Studi “Magna Græcia” di Catanzaro, viale Europa, 88100 Catanzaro, Italy
| | - Carla Giordano
- Sezione di Endocrinologia, DOSAC (Dipartimento di Oncologia Sperimentale ed Applicazioni Cliniche), Università di Palermo, Piazza delle Cliniche 2, 90127, Palermo, Italy
| | - Carlo M. Croce
- Division of Human Cancer Genetics, Comprehensive Cancer Center, Ohio State University, 460 West 12th Avenue, Columbus, Ohio, 43210, USA
| | - Albert de la Chapelle
- Division of Human Cancer Genetics, Comprehensive Cancer Center, Ohio State University, 460 West 12th Avenue, Columbus, Ohio, 43210, USA
| | - Alfredo Fusco
- Istituto di Endocrinologia ed Oncologia Sperimentale del CNR c/o Dipartimento di Biologia e Patologia Cellulare e Molecolare c/o, Facoltà di Medicina e Chirurgia, Università degli Studi di Napoli “Federico II”,80131 Napoli, Italy
- NOGEC (Naples Oncogenomic Center) – CEINGE, Biotecnologie Avanzate, via Comunale Margherita, 482, 80145 Napoli, Italy
- Corresponding Authors Rodolfo Iuliano, Dipartimento di Medicina Sperimentale e Clinica, Facoltà di Medicina e Chirurgia, Università di Catanzaro, Campus “Salvatore Venuta” Viale Europa, località Germaneto, 88100 Catanzaro, Italy. Tel. +39-0961-3695182 Fax: +39-0961-3694090 Istituto di Endocrinologia ed Oncologia Sperimentale del CNR c/o Dipartimento di Biologia e Patologia Cellulare e Molecolare c/o, Facoltà di Medicina e Chirurgia, Università degli Studi di Napoli “Federico II”,80131 Napoli, Italy. Tel. +39-081-3737857 Fax: +39-081-3737808
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12
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Schraders M, Oostrik J, Huygen PL, Strom TM, van Wijk E, Kunst HP, Hoefsloot LH, Cremers CW, Admiraal RJ, Kremer H. Mutations in PTPRQ are a cause of autosomal-recessive nonsyndromic hearing impairment DFNB84 and associated with vestibular dysfunction. Am J Hum Genet 2010; 86:604-10. [PMID: 20346435 DOI: 10.1016/j.ajhg.2010.02.015] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2009] [Revised: 02/02/2010] [Accepted: 02/15/2010] [Indexed: 10/19/2022] Open
Abstract
We identified overlapping homozygous regions within the DFNB84 locus in a nonconsanguineous Dutch family and a consanguineous Moroccan family with sensorineural autosomal-recessive nonsyndromic hearing impairment (arNSHI). The critical region of 3.17 Mb harbored the PTPRQ gene and mouse models with homozygous mutations in the orthologous gene display severe hearing loss. We show that the human PTPRQ gene was not completely annotated and that additional, alternatively spliced exons are present at the 5' end of the gene. Different PTPRQ isoforms are encoded with a varying number of fibronectin type 3 (FN3) domains, a transmembrane domain, and a phosphatase domain. Sequence analysis of the PTPRQ gene in members of the families revealed a nonsense mutation in the Dutch family and a missense mutation in the Moroccan family. The missense mutation is located in one of the FN3 domains. The nonsense mutation results in a truncated protein with only a small number of FN3 domains and no transmembrane or phosphatase domain. Hearing loss in the patients with PTPRQ mutations is likely to be congenital and moderate to profound and most severe in the family with the nonsense mutation. Progression of the hearing loss was observed in both families. The hearing loss is accompanied by vestibular dysfunction in all affected individuals. Although we show that PTPRQ is expressed in many tissues, no symptoms other than deafness were observed in the patients.
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